Kirke,
By 1964 the levers were available with a premium "Red Button" quick release. This was a separate alloy button placed lower on the lever arm which pushed back a tab at the top of the arm.
Here is an example on a Schwinn bike shown in a 1964 dealer catalog, which was the first year this was offered on Schwinns.
http://www.geocities.com/
The push-in tab of the lever shown in your photo is from the early 1970s. They were an alternative to the steel cable hanger mounted quick-release used for center-pull calipers - perhaps desirable when lighter weight was a consideration?
For dating some of the levers by body style you might compare some of these photos.
http://www.flickr.com/
The basic boxy body style gradually acquired a sharper angled contour along the open front edge (beside the lever arm). On earlier models up to the late 1970s this was more square... - as seen in both of your photos.
The milled lever arms were seen on some of the higher end Raleigh bikes during the early 1970s along with the Carlton hoods seen in your second photo. But, I never saw a Raleigh with the extension levers during the early to mid 1970s, so I suspect that may have been a bike shop added option... in the US market.
And, here are some scans of a catalog from around 1973:
http://www.flickr.com/
BOB HANSON, ALBUQUERQUE, NEW MEXICO, USA
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